An efficient, redox-enhanced pair of hydrogen-bond tweezers for chloride anion recognition, a key synthon in the construction of a novel type of organic metal based on the secondary amide-functionalized ethylenedithiotetrathiafulvalene, β"-(EDT-TTF-CONHMe)2[Cl • H2O]

Electrocrystallization of 1,1,2-trichloroethane solutions of the redox-active secondary amide, 3-methylamido-3',4'-ethylenedithiotetrathiafulvalene (EDT-TTF-CONHMe 1) in the presence of n-Bu4NF supported on silica gel afforded a mixed-valence chloride salt, formulated (1)(2)[Cl . H2O] from elemental analysis and X-ray crystal structure resolution. The chloride anion and water molecule are disordered on the same site, and coordinated to the pi-donor molecule by two strong hydrogen bonds involving the amidic N-H and the aromatic C-H group ortho to the amide, thereby qualifying a robust pair of tweezers-like cyclic motif. This efficient anion recognition effect is also observed in solution, as demonstrated by H-1 NMR downfield shifts of both the N-H and C-H hydrogen atom resonances, as well as by a cathodic shift of the oxidation potential of 1 upon Cl- complexation, establishing that the actual electrocrystallized species is a solvated anionic chloride complex [(1 . Cl-)(H2O),1 rather than the free amide. (1)(2)[Cl . H2O] adopts a layered beta "-type structure with segregation of the hydrophobic (EDT-TTF) and hydrophilic (amide, Cl-, H2O) fragments. The HOMO-HOMO intermolecular interaction energies for the donor layers are large and the Fermi surface exhibits a pronounced two-dimensional character. The EPR Dysonian line observed below 120 K indicates an highly conducting system, confirmed by high room-temperature conductivity of 120 S cm(-1) and metallic behavior down to 0.47 K, with a 167-fold increase of the conductivity, but no indication however of a transition to a superconducting state, a likely consequence of the Cl-/H2O disorder.